Manufacture of cellulose material



Patentedv June 18, 1935 UNITED! STATES PATENT OFFICE signor of one-half to Zellstoffi'abrik Waldhof,

Mannheim-Waldhof, Germany, a corporation of Germany No Drawing. Application November 9,

In Germany December 16,

Serial No. 641,947. 1931 i 2 Claims.

Unbleached or slightly bleached cellulose or mixtures thereof with bleached celluloses have a tendency, particularly when stored in damp places or exposed to light, to exhibit intense red- 5 dening or smudged graydiscolorations which are connected with the said reddening. The reddening or discolorations also occur in the fibrous products (paper, cardboard, cellulose wadding and the like) manufactured from such substances and render it impossible or scarcely possible to utilize them for many purposes, particularly since the discoloration or reddening can also be caused V to a considerable extent by the chemical action of various reagents (particularly salts, oxidizing agents and others). This is particularly disadvantageous for example when such papers, say in the form of wrapping paper, come into contact with salt-containing goods.

It has previously been attempted to prevent or eliminate the said disadvantageous reddening and discolorations by means of certain oxidizing agents. This method, however, has been unable to find any introduction into the art, because the use of oxidizing agents is troublesome, and the fibrous material itself is more or less strongly attacked at the same time. It has also been attempted to employ, for the same purpose, volatile reducing agents, such as sulfurous acid, or those which are absorbed either not at all or only a little by the cellulose fibres (for example, hydrosulfite), but without success, because even with these a permanent effect cannot be attained.

I have now found that complete and permanent elimination of this reddening or discoloration occurring with the use of unbleached or slightly bleached cellulose material is attained in a very simple manner by impregnating the material with non-volatile reducing metallic salts which are capable of being absorbed by the cellulose fibre. Salts, such as stannous chloride, cuprous chloride, ferrous chloride, chromous chloride, and like salts, preferably of heavy metals have been found to be particularly adapted for this purpose. Thus, for example, by employing only 1 part of stannous chloride per 1000 parts of unbleached cellulose, it is possible to eliminate the reddening of the cellulose completely and permanently.

The new process may be carried out for as follows:

example Example I In the manufacture of unbleached cellulose, at any point in the manufacturing process which is suitable for a thoroughly good mixing, preferably in the hollander, before finishing, an acid stannous chloride solution is added to the stuff (-1 part of stannous chloride per 1000 parts of dry stuff) The stuff, which immediately becomes considerably lighter in colour, is thoroughly mixed at the same time and is treated further in known manner. It can then be manufactured (also in admixture with bleached cellulose) into perfectly color-fast material such as paper, cardboard, cellulose wadding and the like.

Example II In the manufacture of paper, 1 part of stannous chloride in solution per 1000'parts of dry stuff is added to the ground material in the hollander after the addition of the alumsolution. The ground material is thereupon thoroughly mixed for about 10 minutes, whereupon the treatment is completed' The effect of the addition generally makes itself felt immediately by a considerable lightening in the tint. The material can then be dyed (also in'comparatively pure and clear tints) and worked up in known manner.

I claim:

1. In a process for the manufacture of cellulose material of all kinds from unbleached cellulose, the step of preventing discoloration, particularly reddening of the material which comprises the impregnation of the fibrous material with a solution of stannous chloride.

2. Cellulose materials manufactured from unbleached cellulose and containing stannous chlo- '-ride. a

FRANZ KIEL. 

